1. Field of the Invention
This invention relates to an apparatus for handling banknotes and/or other value documents such as cheques, coupons, etc., which are referred to herein collectively as “banknotes”.
2. Description of Related Art
Banknote handling apparatuses are often required to perform a number of different operations on banknotes, for example causing them to be transported to various positions within the apparatus, measuring their characteristics, storing the banknotes and dispensing the banknotes. Reliable operation depends upon synchronising the operation of the various devices within the apparatus with the position of the banknote which is being handled.
Assuming that a banknote sensor is provided at a particular location in the apparatus, then is is possible, by using a timer, to determine when the banknote reaches further locations within the apparatus, based on the speed of operation of a transport mechanism. This however can be unreliable, because the speed of transport may differ from an expected speed, and may fluctuate.
In some arrangements, this problem is avoided by measuring the time using a clock synchronised to the operation of the transport mechanism (e.g. an encoder coupled to a motor shaft), instead of a fixed frequency clock. However, this arrangement can also be unreliable, for example if there is slippage between the banknote and the drive means (e.g. belts) of the transport mechanism.
To avoid these problems, multiple position detectors may be provided for sensing the banknote as it reaches each of a number of different locations within the apparatus. The position detectors may be optical or mechanical, for example. A substantial number of such detectors may be required, particularly if the apparatus has to perform many functions. In order to reduce the cost and complexity of the apparatus, each position detector is preferably a very simple device arranged to detect a part of the banknote when it reaches a particular position.
A problem encountered with such arrangements is that, if the banknote is torn or folded, or has holes or transparent windows, this could interfere with the operation of the position detector, which can then give a misleading output causing the banknote to be incorrectly handled, and possibly resulting in jamming of the apparatus. For example, banknotes travelling longitudinally along a path may be sensed using a position detector arranged to detect the presence of a banknote at a particular location across its width. However, if the leading edge of the banknote has a piece missing at this lateral location, then the leading edge of the banknote will have passed the location of the position sensor before the sensor output is generated. If it is intended to perform an operation on the banknote at a time dependent on the position sensor output signal, then this operation may start too late, leading to mishandling.
A solution to this problem would be to arrange for the position sensors to sense parts of the banknotes distributed across the entire width thereof. However, this solution would result in increased cost.